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Threat Model Analysis for open-source-parsers/jsoncpp

Threat: Threat: Deeply Nested JSON Denial of Service

  • Description: An attacker sends a JSON payload with excessively nested objects or arrays. The attacker aims to exhaust server resources (stack space or memory) during parsing, causing the application to crash or become unresponsive. This leverages the recursive nature of JSON parsing within JsonCpp.
  • Impact: Denial of Service (DoS). The application becomes unavailable.
  • JsonCpp Component Affected: Reader::parse() (and related internal parsing functions). The core parsing logic that handles object and array nesting is the primary target.
  • Risk Severity: High
  • Mitigation Strategies:
    • Input Validation (Pre-Parsing): Implement a check before calling Reader::parse() to limit the maximum nesting depth. A reasonable limit (e.g., 20-30 levels) should be enforced.
    • Resource Limits: Configure the operating system or application server to limit the memory and CPU time available to the process handling JSON parsing.
    • Timeouts: Implement a timeout for the Reader::parse() operation. If parsing exceeds the timeout, terminate the process.
    • Schema Validation: Use a JSON Schema validator (external to JsonCpp) to enforce a schema that includes a maxDepth constraint.

Threat: Threat: Large Number/String Denial of Service

  • Description: An attacker sends a JSON payload containing extremely large numbers (integers or floating-point) or very long strings. The attacker's goal is to consume excessive memory or CPU time during parsing and conversion within JsonCpp, leading to a DoS.
  • Impact: Denial of Service (DoS). Application unavailability.
  • JsonCpp Component Affected: Reader::parse(), Value::asInt(), Value::asDouble(), Value::asString(), and related internal functions for number and string conversion.
  • Risk Severity: High
  • Mitigation Strategies:
    • Input Validation (Pre-Parsing): Implement checks before calling Reader::parse() to:
      • Limit the maximum length of strings.
      • Limit the maximum and minimum values of numbers.
    • Resource Limits: Configure resource limits (memory, CPU time) as described above.
    • Timeouts: Implement timeouts for parsing and value retrieval operations.
    • Schema Validation: Use a JSON Schema validator with maxLength (for strings) and maximum/minimum (for numbers) constraints.

Threat: Threat: Buffer Overflow Exploitation

  • Description: An attacker crafts a malicious JSON payload designed to trigger a buffer overflow vulnerability within JsonCpp (more likely in older versions). The attacker aims to overwrite memory, potentially leading to arbitrary code execution or data corruption. This might involve malformed UTF-8 sequences or exploiting specific parsing functions within the library.
  • Impact: Remote Code Execution (RCE), Data Corruption, Denial of Service. This is the most severe potential impact.
  • JsonCpp Component Affected: Potentially any part of the Reader or Writer classes, especially functions handling string parsing and manipulation. Specific vulnerabilities would depend on the JsonCpp version.
  • Risk Severity: Critical (if a vulnerability exists), but lower for up-to-date versions.
  • Mitigation Strategies:
    • Keep JsonCpp Updated: This is the most important mitigation. Use the latest stable release.
    • Fuzz Testing: Regularly fuzz test the application's integration with JsonCpp using tools like AFL, libFuzzer, or OSS-Fuzz.
    • Static Analysis: Use static analysis tools to scan for potential buffer overflows.
    • Compiler Flags: Enable compiler security features (stack canaries, ASLR, etc.).
    • Memory Safe Language (if possible): Consider using a memory-safe language for the parts of the application interacting with JsonCpp.